High levels of reacfive oxygen and nitrogen species (ROS/RNS) and type 2 T helper (TH) lymphocyte production of cytokines, such as IL-4 and IL-13, typify asthmafic airway inflammation. Our studies identify a new mechanistic link by which ROS and anfioxidants serve as physiologic regulators of IL-4/IL-13-induced signal transducfion and TH2 responses. The protein tyrosine phosphatase (PTP1B) that physically associates with and dephosphorylates the IL-4/IL-13 receptor is inacfivated by oxidafion, which enables and enhances the TH2 responses of the cell. Further, we show that PTP1B funcfion is restored, and signal transducfion turned off, by specific anfioxidant peroxiredoxins (Prx). Here, we investigate whether this orderly selecfive reducing-oxidizing (redox) activation and inacfivafion of the TH2-cytokine signaling cascade is adulterated under the conditions of excess ROS/RNS and deficient anfioxidants that are well-established to exist in the asthmafic airway. In this context, asthmafic airway epithelial cells synthesize high levels of nitric oxide (NO), which reacts with superoxide to form RNS that cause protein tyrosine nitrafion/inactivafion Using proteomic approaches, we identify that anfioxidant proteins, which attenuate IL-4/IL-13 signal transducfion, are nitrated in the asthmatic ainway, i.e. Prx VI, catalase and Mn superoxide dismutase (MnSOD). New preliminary data also suggest that mitochondria contribute to the excess ROS in asthma; mitochondria in human asthmafic ainway epithelial cells are pathologic on the basis of dysmorphic appearance, increased numbers, loss of mitochondrial MnSOD activity, low cellular ATP &high lactate levels, and low levels of uncoupling protein-2 (UCP-2), a mitochondrial inner membrane protein that acts as a major negative regulator of ROS producfion. Altogether these data support the concept that TH2 pathways may be more easily activated, robust and longer-lasfing in the ROS/RNS-rich, anfioxidant-deficient environment of the asthmatic ainway. Accordingly, Project 1 tests the hypothesis that high levels of ROS/RNS and deplefion of anfioxidants are fundamental determinants of the magnitude and durafion of IL 4/IL-13-mediated ainway epithelial cell signaling and subsequent TH2 responses that drive asthmafic inflammafion. In step with the TPPG goals, we propose mechanisfic aims to uncover knowledge that will translate into innovative care for asthma, e.g. redox-sensitive radionuclide imaging and metabolic diets to reduce mitochondrial ROS producfion. Project 1 draws on the strong complementary skills, unique expertise and resources in the TPPG's fightly synergistic group, and depends heavily upon the shared clinical samples and murine models provided by Cores.